In recent years, small and thin image pickup units are installed on portable terminals of electric devices such as cellular phones or personal digital assistants (PDAs). Such image pickup units generally include a solid-state image pickup device such as a charge coupled device (CCD) image sensor or a complementary metal-oxide semiconductor (CMOS) image sensor and a lens that forms a subject image on the solid-state image pickup device.
Due to downsizing and thinning of portable terminals and popularization of portable terminals, image pickup units mounted thereon are also requested to be downsized and thinned, and high production efficiency is also requested. In response to these requests, a method for mass production of image pickup units is known, whereby a lens substrate on which plural lenses are formed is integrally combined with a sensor substrate on which plural solid-state image pickup devices are formed, and thereafter the lens substrate and the sensor substrate are cut such that each of the cut pieces includes a lens and a solid-state image pickup device. Examples of other production methods include: a method for producing an image pickup unit whereby only lenses are formed on a glass wafer or the like, which is then cut into a size appropriate for combined use with an individual sensor, and then combined with an image pickup device provided on a sensor substrate that has been cut into an appropriate size in advance; a method whereby plural lenses are formed from a resin by using a die, the formed lenses are attached to a sensor substrate, and the substrate is cut; a method for producing image pickup units whereby a lens substrate is cut into a size for combination with an individual sensor, and the cut pieces are combined with an image pickup device provided on a sensor substrate that has been cut into an appropriate size in advance.
Examples of known wafer level lens arrays include those having plural lenses obtained by dripping a curable resin material onto a surface of parallel flat plate substrates formed from a light-transmitting material such as glass and curing the resin material in a state in which the resin material is molded in a predetermined shape in a die (for example, see Japanese Patent No. 3926380 and the pamphlet of International Publication WO2008/102648). In some cases, light-shielding regions formed by a black film, a metal film or the like are formed at areas, other than lens portions, of the wafer level lens, or on a part of lens, in order to control the amount of light. The light-shielding region is generally formed by applying a curable light-shielding composition or depositing a metal.
Other examples of known wafer level lens arrays include a wafer level lens array obtained by forming plural through-holes through a silicon substrate, disposing a separately-formed spherical lens material at each through-hole, adhering the lens material to the substrate by soldering, and further polishing the lens material to form plural lenses (see the specification of U.S. Pat. No. 6,426,829). The lenses obtained by this production method may be provided with a light-shielding region formed by a black film, a metal film or the like similar to the above in order to control the amount of light, depending on the case.
Formation of the light-shielding region by metal deposition has problems in that the processes are complicated, lenses bend after the deposition, or scattering of light occurs due to reflection by the metal light-shielding film; accordingly, improvement is desired from the viewpoints of both of production efficiency and performance.
There are cases in which a photosensitive resin composition (light-shielding composition) in which a carbon black for use in, for example, a black matrix of a LCD is used is applied in order to impart light-shielding property.
Further, a light-shielding film is provided on a solid-state image pickup device such as a charge coupled device (CCD) image sensor or a complementary metal-oxide semiconductor (CMOS) image sensor for the purpose of noise prevention and image quality improvement.
Examples of known compositions for forming light-shielding films for solid-state image pickup devices include a photosensitive resin composition that contains a black colorant such as carbon black or titanium black.
Specifically, photosensitive resin compositions that contain titanium black having a specific X-ray diffraction peak intensity ratio, and that aims at improvement of optical density (for example, see Japanese Patent No. 3724269 and pamphlet of International Publication WO2005/037926), and photosensitive resin compositions that contain titanium black having a specific nitrogen concentration or a specific crystalline diameter (for example, see Japanese Patent Application Laid-open (JP-A) No. 2006-182627, JP-A No. 2006-206891 and JP-A No. 2006-209102) are disclosed.
Further, a composition for forming a light-shielding film that contains titanium black and a resin component, and that aims at obtainment of high light-shielding property with a small film thickness is disclosed (for example, see JP-A No. 2007-115921).